Devices for preparing a beverage by injecting pressurized fluid into a receptacle containing an extractable product are well-known, especially in the field of producing coffee or coffee type beverages. For simplicity, the word coffee is used to refer to beverages obtained when a pressurized fluid is used during the preparation, more in particular espresso and “caffè crema”. The principle of the extraction process, as described in the prior art, can be summarized as follows: the extractable product is inserted in a dedicated chamber, also called receptacle, of a beverage production device. The extractable product can be directly provided to the receptacle which is the case for manual espresso coffee machines. The extractable product can also be provided to the receptacle enclosed in a capsule, a soft or a hard pod according to the used device. The beverage production device comprises at least one fluid injection means for injecting a pressurized fluid, such as water, into the receptacle. The provided fluid interacts with the extractable products contained in the receptacle. As a result of the liquid/solid extraction created in the receptacle, a beverage or other comestible is produced.
For simplicity, we will refer to ground coffee as it's the most used extractable product. However, other comestible ingredients such as chocolate or milk products can also be used with the devices and method of the present invention.
The known methods and devices have several drawbacks. The main drawback is that the extractable material (the ground coffee) introduced in the device for an extraction is not completely used. The incomplete use of the raw material leads to an increase in the used amount per extraction in order to obtain a good beverage. Said incomplete use is explained as follows:
In all known beverage production devices, the ground coffee and its packaging, if available, provide a resistance to the pressurized fluid passage through the receptacle. This leads to the formation of “channels” in the ground coffee powder. Said “channels” represent a preferential way for the pressurized water passage which cannot come into contact with the entire amount of ground coffee present in the receptacle. The amount of ground coffee placed in the receptacle is then only partially used for the preparation of the coffee beverage. This results in a considerable loss of ground coffee and leads to a considerable amount of waste. The liquid under pressure achieves only a partial extraction of all substances of the ground coffee to the detriment either of the quality of the coffee or of the quantity of coffee powder to be used, ending in a higher quantity of coffee.
An additional drawback is the variability of the resulting beverage. This results from the fact that the resistance provided by the ground coffee is itself dependent on different variable parameters. Said parameters comprise: the compression degree of the raw material (ground coffee), its blending, its roasting and its grinding. For instance, in the espresso manual devices, the user fills the receptacle and compresses the ground coffee using a tamper. The compression level of the ground coffee will depend on the physical condition of the user which is variable according to the user but also variable during time for the same user. When the ground coffee is contained in a packaging, be it a capsule, a soft pod or a hard pad, the resistance depends on the grinding and the compression level of the coffee.
Some attempts were made to allow the exploitation of the entire amount of solid substance present in the receptacle, during the liquid/solid extraction and thereby provide infusions with better quality. The attempts are described in EP 1 016 364, EP 0 622 039 and EP 2 036 469 disclosing devices (percolator cups) used in espresso machines.
The described devices are all provided with at least one spring and are based on the same principle. Said spring is pre-loaded in compression and is used as to provide a back pressure to a valve plate. When the pressure in the receptacle exceeded the pressure applied by the spring on the valve/plate, infusion is allowed to flow out of the percolator.
These devices also present several disadvantages such as having a complex design. Said design is only used for espresso machines and cannot be applied in other beverage production devices. A possible damage or fatigue of the spring will influence the pressure threshold at which the infusion can flow out of the device. Moreover, in these devices, the spring will close the valve/plate at the end of the brewing phase. Droplets of infusion might be still present in the receptacle and/or on top of the valve/plate. These droplets remain in the device which is not hygienic, creates dirt and a bad smell in the device. Said droplets will be part of the next performed extraction which, on one hand, considerably lowers the taste of the obtained beverage and, on the other hand, is not healthy for the consumer.
The aim of the present invention is to provide a solution to overcome at least part of the above mentioned disadvantages. The method and devices of the present invention aim to provide a uniform liquid/solid extraction by providing a full control of the pressure inside the receptacle of the beverage production device. The invention is disclosed in the claims.